问

如何使用Dynamic LINQ使用GroupBy

重庆车管所发布于 2023-02-13 13:57

list

int

foreach

select

我正在尝试使用动态LINQ进行GroupBy,但无法使其工作.

这是一些说明问题的示例代码:

List listAlbums = new List();
for (int i = 0; i < 5000; i++)
{
    dtoMyAlbum album = new dtoMyAlbum
    {
        Author = "My Author",
        BookID = i,
        CurrSymbol = "USD",
        Price = 23.23,
        Shop = i % 3 == 0 ? "TESCO" : "HMV"
    };
    listAlbums.Add(album);
}

IQueryable mydata = listAlbums.AsQueryable();
int count = mydata.Count();

//var mydataGrouped = mydata.GroupBy(a => a.Shop);      // <-- this works well (but is not dynamic....)
var mydataGrouped = mydata.GroupBy("Shop");             // <-- does not compile but is kind of what I want...

foreach (var group in mydataGrouped)
{
    //count = group.Count();
}

我意识到我在GroupBy重载中缺少'elementSelector',但我想做的就是最终得到(在这种情况下)两组dtoMyAlbum对象,所以我希望为所有集合选择所有元素......

我该怎么做？

1 个回答

默认it定义,您可以使用它来返回匹配的元素:

var mydataGrouped = mydata.GroupBy("Shop", "it");

要遍历结果,您还应该使用其他Select元素命名并使用dynamics:

var mydataGrouped = mydata.GroupBy("Shop", "it").Select("new (it.Key as Shop, it as Albums)");

foreach (dynamic group in mydataGrouped)
{
   foreach (dynamic album in group.Albums)
   {
      Console.WriteLine(album.Author);
   }
}

2023-02-13 13:59 回答

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